Adhesives for bonding composites

ABSTRACT

Adhesive composition, including a mixture of about 1 percent to about 35 percent by weight of chlorinated polymer, about 1 percent to about 35 percent by weight of a nitrile elastomer, a rubber-modified acrylonitrile copolymer, or mixtures thereof, and about 25 percent to about 90 percent by weight of an alkyl acrylate or methacrylate monomer.

BACKGROUND OF INVENTION

[0001] 1. Field of Invention

[0002] This invention relates to adhesives. More particularly, thisinvention relates to two-part room-temperature curing methacrylate basedadhesives that are used to bond a wide variety of materials, includingthermoset plastics, thermoplastics, metals, wood, ceramics and othermaterials and combinations of materials. This invention involves asignificant improvement in the ability of adhesives to bond certaindifficult-to-bond composite materials with minimum required surfacepreparation. Another feature of this invention is the high degree ofelastic behavior of the cured adhesives and the ability of the curedadhesive materials to retain a high proportion of their elastic behaviorafter exposure to elevated temperatures or long-term aging.

[0003] 2. Background Art

[0004] The three common classes of two-part room temperature curingreactive adhesives are epoxies, polyurethanes, and acrylics. Thediscussion of these prior art adhesives and the inventive adhesivesemphasizes structural applications, wherein a very strong bond isachieved between two structural members of an assembly, and the bond isoften strong enough to cause failure of the material before the assemblyfails. However, all of these adhesive materials, can be and are used toadvantage in less demanding applications, as well, in which case one ormore of the advantages of the particular adhesive fulfills a specificbonding requirement.

[0005] Epoxy adhesives, which are the earliest, best known and among themost common structural adhesives in general use, consist of an epoxyresin adhesive component and an amine, polyamide, or combined amine andpolyamide hardener components. Faster curing epoxies can be formulatedwith polymercaptan hardeners that are generally used in combination withpolyamide and amine hardeners.

[0006] Polyurethane adhesives generally consist of anisocyanate-terminated polyol and a hardener or curative component thatconsists of a polyol or amine or a combination of polyols and amines.

[0007] The epoxy and polyurethane adhesives cure upon mixing when thehardener component reacts with the epoxy or polyurethane resin componentin an addition polymerization process.

[0008] Methacrylate or acrylic adhesives that are used in the sameapplications as epoxies and polyurethanes generally consist of apolymer-in-monomer solution of an elastomer or thermoplastic resin or acombination thereof in a monomer such as methyl methacrylate. Hardeningis achieved when a combination of a peroxide and an amine is introducedinto the polymer-in-monomer mixture to initiate a free-radical curingreaction. Generally, the adhesive component contains either the amine orperoxide component and the co-reactive peroxide or amine component ismixed with the adhesive just prior to bonding.

[0009] Each of the three common reactive adhesive classes hascharacteristic advantages and disadvantages. For example, epoxies tendto be characterized as safe and relatively easy to mix and apply, buttend to be somewhat rigid and sensitive to cleanliness of the surface tobe bonded. Polyurethanes are generally considered to be much moreflexible and elastic, but also suffer from sensitivity to surfacecontamination, moisture and humidity. Both of these adhesive types havethe limitation that fast-curing products tend to have very short openworking time after mixing, and products with more acceptable open timehave very long cure times. This limitation is imposed by the linearreaction mechanism that is characteristic of the addition polymerizationreaction by which they cure.

[0010] In terms of the characteristics of the cured adhesive andresulting bond, epoxies are considered to be very strong because oftheir high modulus or rigidity and resulting high lap shear strength.They are generally recommended for bonding metals because of theiraffinity for metal surfaces and high shear strengths. However, theirrigid nature limits their usefulness in applications that requireflexibility in the adhesive bond. Epoxies also have limited ability tobond thermoplastic materials.

[0011] Polyurethanes are generally much more elastic, tough and flexiblethan epoxies. Elasticity, toughness and flexibility are beneficial whenadhesive bonds are subjected to peeling or impact forces, and when bondsand bonded assemblies are subjected to dynamic fatigue stresses.However, polyurethanes are not as useful as epoxies for bonding metals,and are generally more suitable for bonding plastic materials inapplications that are subjected to bending and impact stresses.

[0012] Two-part acrylic or methacrylate adhesives overcome two of themajor drawbacks of the epoxies and polyurethanes. They are much moretolerant of unclean or unprepared surfaces, and they have a much morefavorable cure profile in terms of open working time and cure rate. Inaddition, they exhibit equal or better affinity for metal and plasticsurfaces than either epoxies or polyurethanes. However, some materials,in particular certain composite materials, are difficult to bond in the“as received” condition. Specific examples include certain gel coats,which are highly crosslinked and inert polyester compounds that form theouter or “show” surface of fiberglass reinforced polyester (FRP)composite materials used to fabricate boats and other structures exposedto outdoor weathering.

[0013] Other examples are closed molded polyester composites, which arematerials formed by processes other than the open molded processes usedto produce FRP composite structures. Examples of closed moldingprocesses and materials are sheet molding compounds (SMC), resintransfer molded (RTM) composites and pultruded composites.

[0014] The essential issues with closed molded processes and productsare (1) these processes produce polyester composite articles withreduced emission of and worker exposure to the styrene component inpolyester resins and are rapidly replacing open molded processes, and(2) these materials are generally characterized by resistance to thesolvating effect of the methacrylate monomers that normally soften orpenetrate the bonding surface prior to hardening of the adhesive. Inaddition, many of these materials use processing aids to provide smoothsurfaces for painting. These materials can also interfere with thebonding process.

[0015] Other materials are used to facilitate release from the moldsused to fabricate parts from them. Such materials are often addeddirectly to the molding compound, in which case they are referred to as“internal” mold releases. Other materials may be sprayed on to the moldsurface prior to molding. These materials are referred to as “external”mold releases. All of these processing aids can interfere with theformation of strong adhesive bonds.

[0016] The problems experienced in bonding these materials with priorart methacrylate-based adhesives, as well as the additional andundesirable processing steps required to use them, includinggrit-blasting, sanding, solvent wiping and priming are described indetail in U.S. Pat. No. 3,838,093, which is discussed in further detailbelow.

[0017] Epoxy adhesives based on standard DGEBA (diglycidyl ether ofbisphenol-A) resins, cured with hardeners based on combinations ofamines, polyamides and other additives used to impart specificproperties, have effectively been used to bond some closed moldedcomposite materials. However these adhesives do not completely cure atroom temperature, and generally require thermal post-curing to developtheir full physical strength.

[0018] Recent developments in polyurethane adhesive technology have beendirected toward improving adhesion to these composite materials asdisclosed, for example, in U.S. Pat. Nos. 5,340,901 and 5,548,056.However, as with epoxy adhesives, these materials often require thermalpost curing. Even though polyurethanes do ultimately develop their fullphysical strength at ambient temperatures, such post curing may berequired to meet process speed requirements or to develop full, reliableor reproducible adhesion to the composite surface, or both. In somecases, solvent-based primers are used to develop adhesion at ambienttemperatures, but this is undesirable for environmental and healthreasons.

[0019] Yet another problem with the epoxy and polyurethane-basedadhesives is their limited ability to bond to open-molded compositesurfaces. Open-molded composite articles are fabricated by using acombination of spraying and rolling processes that combine woven andchopped fiberglass with polyester laminating resins in open molds. Amold in the shape of the article is first sprayed with a gel or outercoat of a highly crosslinked, pigmented resin that creates a smooth,shiny exterior or “show” surface. The laminating resin and glass arethen applied together in successive applications until the desired partthickness is achieved. It is desirable to be able to de-mold the moldedarticle as quickly as possible and move it on to the assembly area. Atthis point, and for several hours thereafter, the resin is notcompletely cured and is referred to as “green” as the final stage of thepolymerization process proceeds. In this state, the exposed or “raw”resin surface is difficult or impossible to bond with conventional epoxyor polyurethane adhesives.

[0020] Thus, while epoxies and polyurethanes are sometimes capable ofbonding the gel coat or show surfaces of these resin structures, in mostcases it is necessary to bond the raw surface to itself or to the gelcoat surface. Methacrylate adhesives have been increasing in popularityand usage because of their ability to bond the raw fiberglass surfaces,even in the green state. However, as improvements and changes have beenmade in the composition of the gel coat materials in recent years, theability of the methacrylates to bond them, especially in the “asreceived” condition, has become less predictable.

[0021] A significant characteristic of some of the more recent acrylicsor methacrylates is elasticity, toughness and flexibility that isgreater than that of epoxies and even approaches that of thepolyurethanes. However, not all of the methacrylate adhesives exhibitsuch elasticity, toughness and flexibility initially, and many of thosethat do often fail to retain these properties over a long period of timeor when heated to elevated temperatures. Such reduction in elasticitycan be demonstrated by comparing the bulk stress-strain properties offilms prepared from the compositions which have not been exposed toelevated temperatures with similar films that have been subjected tobrief or prolonged exposure at various temperatures. Loss of elasticitythat occurs upon brief exposure at elevated temperatures may be theresult of a continuation of the curing process, or a “post curing”process. It is also believed that certain physical changes in the phasedistribution of the glassy and rubbery components or domains can occurin the cured composition when it is heated to or above its glasstransition temperature or Tg. Loss of elasticity that occurs uponprolonged exposure to elevated temperature can also be the result ofeither the post curing or physical processes described above or thechemical degradation because of oxidative or other thermally inducedreactions that adversely affect the polymer structure.

[0022] The improvements of this invention are primarily directed towardchanges that occur as a result of post curing or physical changes afterrelatively brief exposures to elevated temperatures or longer exposuresto ambient temperatures. Resistance to oxidative or other thermaldegradation processes is subject to other chemical formulatingprinciples well known to those skilled in the art.

[0023] Practical manifestations of these phenomena include the potentialloss of the ability of adhesive bonds to resist peeling or impact forcesas the bonded assembly ages, or a reduction in the elasticity orincrease in hardness of the cured composition in the center portion of athick cross section. The latter is believed to occur when the exothermalheat generated by the polymerizing composition raises the temperature toa level that approaches or exceeds the Tg of the cured composition.Whatever the cause of the physical changes that occur during or afterthe initial curing phase of the adhesive, the ultimate physical andelastic characteristics of the adhesive can generally be predicted by abrief exposure of the material in question at an elevated temperature.Typical thermal exposures for this purpose are from 30 minutes to a fewhours at temperatures ranging from about 70 degrees centigrade to about100 degrees centigrade.

[0024] As the use of adhesives increases in the fabrication of compositestructures, design engineers are increasingly aware of the need toreliably predict the physical characteristics of the adhesives, whichbecome an integral part of the structure. In this regard, adhesives aregenerally characterized by their tensile strength, modulus or stiffness,and elastic properties. In some cases, a stiffer adhesive is desired inorder to provide a high degree of load bearing capability in the bondedjoint. In other cases, a more flexible or elastic joint may be requiredin order to resist shock, vibration and fatigue loads. In civilengineering applications, such as highway bridge construction, asomewhat stiffer bond may be desirable. However, it is important thatthe adhesive also have a predictable degree of elastic behavior in orderto withstand the bond stresses that occur as a result of thermal cyclingand the resulting differential expansion of the bonded components. It isalso necessary to withstand the cyclic loading of the structure imposedby vehicular traffic on the bridge. In extreme cases, seismic loads oncivil engineering structures demand the utmost in stress to failurecapability of the adhesive and the resulting joint.

[0025] In the fabrication of boats, on the other hand, more flexibleadhesives are often desirable. An example is the bonding of stringers orliners in the structural fabrication of the boat hull. In thisapplication, there can be a combination of severe shear, peel, and shockloading of the bonds when the boat is operated at high speeds over roughor choppy water. Flexible adhesives can provide very durable joints byresisting the peel and shock loads imposed on the bond and by dampingthe energy transferred to the joint as it undergoes cyclic loading.

[0026] In all of these cases, it is imperative that the adhesive becapable of retaining the physical characteristics, especially theability to withstand shock and fatigue loads, during the lifetime of thestructure. It is further important that the components of the adhesivecan be adjusted to provide the desired degree of stiffness andflexibility for a variety of applications.

[0027] It is clear from the discussion above that there is a need foradhesives that will reliably and predictably bond a wide variety ofcomposite surfaces in the as received condition, rapidly and without theapplication of heat to complete the cure or develop full adhesive bondstrength. It is also desirable for such adhesives to bond otherstructural materials such as metal, thermoplastics, wood, etc. It isfurther desirable that such adhesives possess a high and predictabledegree of elasticity and retain their elasticity when exposed toelevated temperatures during the curing process or in service.

[0028] The benefits derived from the improvements of this inventionapply to structural adhesive bonding applications. However, thecompositions disclosed herein may also be useful in a number of otherapplications for which epoxy, polyurethane, methacrylate and polyesterresins are employed. One such application is coatings. A specificexample of a coating is the driving surface of bridge decks, includingFRP or composite bridge decks which may be fabricated and assembledusing adhesives, including the adhesive compositions of the presentinvention. Such coatings are often referred to as bridge deck overlays.

[0029] FRP or composite bridges and bridge decks have been developed toreplace traditional steel and concrete structures for a number ofreasons, including their resistance to rust and decay in severeclimates. Their light weight and high strength relative to steel andconcrete structures make them especially useful for reconstructing aged,deteriorated bridge structures. Composite decks can be used to replacethe existing concrete and steel deck of a deteriorated structure withoutreplacing the entire structure. The light weight and equivalent orsuperior load-bearing capability of the composite deck allows the bridgeto support the same traffic loads as the existing structure withoutreplacing other deteriorated structural support members of the bridge.

[0030] Reconstructed bridges, as well as new and replacement bridges canbe installed more quickly and with less traffic disruption thantraditional bridges. Other benefits of this concept are too numerous tomention and beyond the scope of this invention. However, a commonproblem with these applications is the final step of replacing thepavement or driving surface of the bridge deck.

[0031] Existing bridge resurfacing materials are generally composed ofpolymer latex modified concrete or an aggregate composition that uses anepoxy resin or polyester resin as a binder for the aggregate andadhesive to secure the surface to the bridge deck. These materials wereoriginally developed and have been used for resurfacing traditionalconcrete or asphalt bridge decks. Application of these materials tocomposite bridge decks has been less than satisfactory for a number ofreasons, including mismatched coefficient of thermal expansion relativeto the composite deck, insufficient toughness and flexibility, poor ormarginal adhesion, and complexity in mixing and application.

[0032] The benefits of the present invention for adhesives, namelyelasticity and toughness, and the retention of elasticity and toughness,combined with the ability to bond a number of surfaces, includingdifficult to bond composites, are useful for replacement of the drivingsurface of the bridge as well. Their toughness, flexibility andresistance to cracking also provide potential benefits for overlaycoatings for restoration of existing concrete and asphalt bridge decksurfaces. In this case, the coating can perform both as a traffic wearsurface and as a sealant to prevent intrusion of moisture, salt andother damaging elements that can damage the concrete and metal bridgestructure beneath the pavement. For this application, it is imperativethat the coating be resistant to cracking or any other loss of integritythat allows moisture or damaging agents such as deicing chemicals, oilsor fuels to penetrate the coating. Such penetration can eventually leadto disbondment of the overlay and or damage to the structural componentsof the bridge deck and supporting structures.

[0033] U.S. Pat. No. 3,333,025 discloses improvements in the adhesiveproperties of polymerizable adhesives based on mixtures of methylmethacrylate monomer, styrene monomer, polychloroprene, and optionallyan unsaturated polyester resin.

[0034] U.S. Pat. No. 3,838,093 describes problems associated with thebonding of fiberglass reinforced polyester (FRP) substrates withadhesives, including the adhesives of the '025 patent. It furtherdiscloses compositions of primers based on isocyanate and polyolcomponents as primers, wherein the primers require volatile organicsolvents in order to be effectively applied. It further discloses therequirement to cure the primer by allowing it to stand at ambienttemperatures for up to 72 hours, or by baking the primed substrate in anoven at 200-280 degrees F.

[0035] U.S. Pat. No. 3,890,407 discloses methacrylate adhesives withimproved adhesive properties comprising mixtures of chlorosulfonatedpolyethylene (CSPE) in methyl methacrylate (MMA) monomer. Among thecompositions disclosed are mixtures of Hypalon 20 and Hypalon 30 CSPE inMMA with other additives to complete the adhesive formulations. Amongthe improvements cited are increased speed of cure, improved adhesion tounclean or unprepared surfaces, and high bond strength.

[0036] U.S. Pat. No. 4,126,504 discloses methacrylate monomer basedadhesives containing a variety of polymers, including polychloroprene,chlorosulfonated polyethylene, and butadiene/acrylonitrile. It suggeststhat mixtures of such polymers may be employed, but does not cite orclaim specific mixtures or combinations of polymers or suggest ordisclose specific advantages obtainable through the use of suchmixtures. In particular, it does not suggest mixtures of polychloropreneor chlorinated polyethylene polymers with butadiene-acrylonitrilepolymers.

[0037] U.S. Pat. No. 5,206,288 discloses methacrylate adhesives based onmixtures of a number of elastomers blended individually with acore-shell impact modifier. These adhesives exhibit a high degree oftoughness and flexibility, especially at low temperatures.Polychloroprene and butadiene-acrylonitrile elastomers are disclosedindividually in combination with the core-shell impact modifiers, butthere is no suggestion of employing blends of these elastomers incombination with the impact modifiers.

[0038] It has now been discovered that unique and highly beneficialadhesive characteristics can be achieved by blending chlorinatedpolymers such as polychloroprene, chlorinated polyethylene andchlorosulfonated polyethylene with butadiene-acrylonitrile elastomersand methacrylate monomers and free-radical catalysts to formpolymerizable methacrylate adhesives. Such adhesives display excellentadhesion to difficult-to-bond composite surfaces, without the need forextensive surface preparation. Moreover, the adhesives exhibit a highdegree of elasticity and retain their elasticity following exposure toheat.

SUMMARY OF INVENTION

[0039] The adhesives of the invention encompass a combination of about 1to about 45 percent by weight, preferably from about 2 percent to about35 percent by weight, most preferably from about 5 percent to about 25percent by weight of a chlorinated polymer, preferably a chlorinatedelastomer polymer, about 1 percent to about 45 percent, preferably fromabout 1 percent to about 25 percent, and most preferably about 1 percentto about 20 weight percent by weight of a nitrile elastomer, arubber-modified acrylonitrile copolymer or mixtures thereof, and about25 percent to about 90 percent by weight of an alkyl acrylate ormethacrylate monomer, preferably a C₁ to C₅ alkyl acrylate ormethacrylate monomer.

[0040] In a further preferred embodiment, the adhesives of the inventionencompass a combination of about 1 percent to about 45 percent,preferably from about 5 percent to about 25 percent, of a chlorinatedelastomer polymer, about 1 percent to about 45 percent, preferably fromabout 1 percent to about 25 percent of a nitrile elastomer, from about0.01 to about 30 percent, preferably from about 0.01 to about 20 percentof a core-shell impact modifier in combination with a methacrylatemonomer or a mixture of methacrylate monomers. The preferred monomersare C₁ to C₅ alkyl acrylate or methacrylate monomers which constitutefrom about 25 percent to about 90 percent by weight, preferably fromabout 40 percent to about 90 percent by weight, and most preferably,from about 50 percent to about 85 percent by weight of the composition.The most preferred monomer is methyl methacrylate monomer. Additionaluseful monomers are C₆ or higher methacrylate monomers which canconstitute from 0.01 to about 25 percent, and preferably from 0.01 toabout 15 percent of the composition. The compositions may also containfrom 0 to about 15 percent, preferably from 0.01 to about 10 percent ofa polymerizable organic acid monomer. The compositions are cured with afree radical generating catalyst system.

[0041] The preferred monomers of the invention are alkyl methacrylatemonomers, but other monomers such as, for example, acrylate monomers mayalso be used to advantage in the compositions. Similarly, methacrylateor acrylate monomers other than alkyl methacrylates may be used invarying proportions to impart specific properties, as may be othercompatible, polymerizable vinyl monomers including styrene and monomersderived from styrene.

[0042] The adhesive compositions of the inventions are characterized bytheir ability to bond a variety of composite materials, includingcertain difficult to bond composites with or without preparation of thesurface prior to bonding, as well as a variety of other materials aloneor in combination. The adhesives are further characterized by their highdegree of elasticity and their ability to retain their elastic behaviorafter exposure to elevated temperatures or long term aging under ambientconditions.

DETAILED DESCRIPTION OF INVENTION

[0043] The essential feature of this invention is the use of acombination of a chlorinated polymer, preferably a chlorinatedelastomeric polymer, and a copolymer of acrylonitrile with butadiene orisoprene, or a combination of butadiene and isoprene, as the elastomericcomponent of a methacrylate-based adhesive.

[0044] The preferred chlorinated elastomer polymers of this inventionare polychloroprene, chlorosulfonated polyethylene, chlorinatedpolyethylene, other chlorinated hydrocarbon polymers, chlorinatedrubber, epichlorohydrin polymers, or other polymers containing fromabout 20 to about 55 percent chlorine, and preferably from about 25 toabout 45 percent chlorine. Examples of preferred chlorosulfonatedpolyethylene polymers are Hypalon 20, Hypalon 30, Hypalon 40, andHypalon 48. Examples of preferred chlorinated polyethylene polymers areTyrin 3615, Tyrin 4211, and Tyrin 4215. Examples of preferredpolychloroprene polymers are Neoprene AD-5, AD-10, AD-20, and otheradhesive and non-adhesive grades of polychloroprene polymers. All ofthese preferred chlorinated polymers are available form DuPont DowElastomers among other commercial manufacturers.

[0045] Chlorinated polymers such as polyvinyl chloride (PVC) or vinylchloride copolymers such as vinyl chloride/vinyl acetate copolymers mayalso be employed. Unmodified polyvinyl chloride is not readily solublein the methacrylate monomers of this invention, but may be dispersedunder conditions of high shear. The copolymers, on the other hand arereadily soluble. Another useful method of incorporation of polyvinylchloride polymers is the addition of nitrile elastomer/PVC blends. Suchblends, which typically contain from about 20 percent to about 80percent, and preferably from about 30 percent to about 70 percentnitrile elastomer are sold by Zeon Chemicals under the trade name Nipol.Specific examples are Nipol P-70, a 70/30 nitrile-PVC blend, and Nipol503 F1, a 50/50 blend.

[0046] The nitrile elastomer polymers of the instant invention arebutadiene-acrylonitrile or butadiene-isoprene-acrylonitrile polymerswith an acrylonitrile content from about 15 to about 50 percent,preferably from about 18 to about 45 percent. The remainder of thenitrile polymer backbone is typically butadiene or a combination ofbutadiene and isoprene. The glass transition temperatures (T_(g)) of thepolymers range from about −50 to about 0 degrees C., and preferably fromabout −40 degrees C. to about −10 degrees C. Examples of such polymersinclude polymers available from Zeon Corporation, such as Nipol DN401LL, Nipol DN 1201L, Nipol 1401LG, Nipol 1472 and Nipol DN 4555.

[0047] Certain rubber-modified acrylonitrile copolymers includingacrylonitrile-butadiene-styrene (ABS) andmethacrylate-acrylonitrile-butadiene-styrene (MABS) solution or moldinggrade resins are also useful components of this invention, but theyusually are most effective when used in combination withbutadiene-acrylonitrile or butadiene-isoprene-acrylonitrile elastomers.Solution grade or molding grade resins that are useful in conjunctionwith the chlorinated and nitrile elastomers of this invention typicallycontain from about 5 to about 50 percent, preferably from about 5 toabout 30 percent butadiene, the remainder of the polymer primarilycomprising styrene and acrylonitrile, or styrene, acrylonitrile andmethyl methacrylate. Other styrenic or vinyl monomers may also beemployed. The range of compositions of the polymers and a description ofthe various processes used to prepare them are described in U.S. Pat.No. 4,233,418.

[0048] One useful ABS resin is Blendex ADG-21 supplied by GeneralElectric. It is a solution grade resin sold for the manufacture ofsolvent cements for ABS pipe. It contains about 35.5 percentacrylonitrile, about 7.5 percent butadiene and about 60 percent styrene.A useful MABS resin Terlux 2812 TR from BASF, a specialty clear gradesold for molding applications requiring a high degree of clarity andretention of physical properties. It has a density of 1.08 g/cc, tensilestrength of 5,988 psi and tensile modulus of 278,200 psi. It is evidentfrom the range of ABS and MABS polymers that are useful in thisinvention that these examples should not be limiting. For example, ABSand MABS solution and molding grade resins typically contain asubstantial portion of free styrene acrylonitrile copolymer (SAN)copolymer, and thus the SAN copolymer is an effective component as well.

[0049] When used, these polymers are incorporated in amounts from 0.01to about 30 percent, preferably from about 2 to about 25 percent of theadhesive composition.

[0050] Other polymeric materials may be used to advantage in thecompositions of this invention. For example, core-shell impact modifiersmay be used to impart desirable non-sagging Theological characteristics,and may also impart other desirable adhesive or mechanical propertycharacteristics. Examples of such polymers are MABS, ABS, or MBS polymerimpact modifiers of the core shell type. The MBS polymers are similar tothose described in U.S. Pat. No. 4,304,709, which is hereby incorporatedby reference. The MBS polymers are generally made by polymerizing methylmethacrylate monomer and styrene in the presence of polybutadiene or apolybutadiene copolymer rubber.

[0051] ABS and MABS impact modifiers are made by a similar processwherein the methyl methacrylate monomer is replaced by acrylonitrile ora combination of acrylonitrile and methyl methacrylate monomer,respectively. These polymers are described in U.S. Pat. No. 4,513,108which is hereby incorporated by reference. An example of an ABS impactmodifier is Blendex 338 produced by General Electric Company.

[0052] Another optional feature of this invention is the use of a mixedacrylate or methacrylate monomer composition. While the primarycomponent of the monomers will be methyl or ethyl methacrylate or otheracrylates or methacrylates with five or less carbon atoms in the alcoholportion, these monomers may be combined with longer chained monomerssuch as the C₆ and greater acrylates or methacrylates. The mostpreferred longer chain acrylates and methacrylates are dodecyl (C₁₂,also known as lauryl) and stearyl methacrylates, may be based on linearaliphatic alcohols. Other preferred monomers of this group are n-hexyln-octyl, n-decyl, octadecyl, and other similar monomers with analiphatic alcohol group of up to about 24 carbon atoms. The relativeamounts of the short chain and long chain acrylate or methacrylatemonomers that are used in the compositions depend upon the particularend use.

[0053] The longer chain methacrylate monomers generally increase theflexibility and toughness of the cured adhesive composition. They canalso affect the adhesive characteristics of the composition byincreasing or decreasing the affinity of the adhesive composition towarda particular substrate or group of substrates. In general, higher levelsof methyl methacrylate provide higher modulus and stiffness and reducedtoughness and flexibility. The amount of longer chain monomer isselected to achieve the desired level of flexibility and toughness,without unduly reducing stiffness and modulus. Similarly, the amount oflonger chain methacrylate monomer is selected in such a way as toachieve the desired adhesion characteristics without unduly andnegatively affecting other desirable adhesive characteristics.

[0054] Another function of the long chain acrylic or methacrylatemonomer is to extend the open time of the adhesive by reducing thevolatility of the monomer mixture. To further extend the open time,natural or synthetic waxes may be added in amounts ranging from about0.1 to 2 percent or more. The addition of such waxes further extendsopen time by acting as a barrier to reduce the rate of evaporation ofmonomer from the surface of the wet adhesive layer.

[0055] The preferred monomers of the invention are alkyl methacrylatemonomers. However, acrylate monomers may also be used to advantage inthe compositions. Similarly, methacrylate or acrylate monomers otherthan alkyl methacrylates may be used in varying proportions to impartspecific properties. Examples of other useful monomers are hydroxylsubstituted monomers such as hydroxyethyl and hydroxypropyl methacrylateand acrylate, tetrahydrofurfuryl acrylate and methacrylate, cyclohexylmethacrylate and methoxyethyl methacrylate. Difunctional crosslinkingmonomers and oligomers, including those derived from epoxy andpolyurethane backbones can also be used to advantage in thecompositions. The general selection of available monomers and oligomersis well known to those in the art and is reviewed in U.S. Pat. No.5,935,711.

[0056] When used, the monomers, other than the C₁-C₅ alkyl acrylates andmethacrylates, are added in amounts ranging from about 0.01 to about 25percent of the polymer and monomer composition, preferably from about0.5 to about 15 percent.

[0057] In order to further promote adhesion, especially to metals, thepresence of a polymerizable acid such as methacrylic acid is preferred,in amounts ranging from about 0.01 to about 15 percent based on thetotal composition. Other useful polymerizable acids are acrylic acid,maleic acid, itaconic acid, and other copolymerizable unsaturated acidsof this type that are well known to those skilled in the art.

[0058] In order to control the viscosity of the adhesive, variousviscosity control agents such as organoclays, fumed silica or the likemay be added in amounts ranging from about 0.1 to about 10 percent basedon the system weight. Additional fillers may be added in significantlylarger amounts to reduce the cost of the adhesive or to modify certainphysical properties such as shrinkage and exotherm characteristics. Inthis case, quantity of the filler or extender would be consideredseparately as an additive to the base polymer and monomer composition asdescribed above.

[0059] Common particulate fillers or extenders such as clay, talc,calcium carbonate, silica and alumina trihydrate can be added in amountsup to about 50 percent or more of the composition by weight in order toachieve specific economic, application or bonding characteristics.Inorganic or organic microspheres or microballoons may be used to reducethe density and cost of the adhesives, as well as to improve theirsanding or finishing characteristics when used as repair materials suchas automobile body repair products.

[0060] Any number of available and well-known catalysts may be chosen tocause the polymerization and curing of the compositions of the instantinvention. The terms used to describe the various components of thecuring system (catalysts, initiators, activators, promoters) are oftenused interchangeably, and thus the terminology used below may differfrom other descriptions used in the art.

[0061] Generally, the catalyst chosen is a free radical generatingcatalyst. Examples of these catalysts are benzoyl peroxide, cumenehydroperoxide, tertiary butyl hydroperoxide, dicumyl peroxide, tertiarybutyl peroxide acetate, tertiary butyl perbenzoate, ditertiary butylazodiisobutyronitrile and the like. These free radical producingcatalysts are used in amounts of about 0.01 to about 10 weight percentbased on the weight of the adhesive composition. Preferably, thecatalysts will be used in the amount of about 0.05 to about 5 weightpercent.

[0062] Other components that promote or enhance the reactivity of thecatalysts are initiators or activators and promoters. The initiators oractivators are added in the amount of up to about 15 weight percentbased on the weight of the adhesive. Preferred amounts are 0.01 to about5 percent. Initiators and activators, which terms are often usedinterchangeably, include tertiary amines and aldehyde-amine reactionproducts. Useful tertiary amines include N,N-dimethylaniline,N,N-diethyltoluidine, N,N-bis(2-hydroxyethyl) toluidine and the like.

[0063] Aldehyde-amine reaction products include such compositions asbutyraldehyde-aniline and butyraldehyde-butylamine derivatives whoseactive ingredient is a dihydropyridine (DHP) formed from condensation ofthree moles of aldehyde with one mole of amine. More recently,DHP-enriched versions of these compositions have been made available.One such material is Reillcat ASY-2, available from Reilly Industries,Inc. This catalyst or initiator system is most often used in combinationwith a sulfonyl chloride compound and a hydroperoxide as described inU.S. Pat. Nos. 3,890,407 and 4,182,644.

[0064] Compositions utilizing chlorosulfonated polyethylene, ahydroperoxide such as cumene hydroperoxide, and DHP as thecatalyst/initiator system are generally mixed and applied in one of twoways. One is to include the chlorinated polyethylene and hydroperoxidealong with all other adhesive components in a single polymer-in-monomercomposition. The DHP can be applied to the bonding surfaces by brushing,rolling or spraying, which was the preferred method disclosed in theabove-referenced '407 patent. The most popular current commercial methodof use is to formulate a 1:1 mix ratio adhesive wherein thechlorosulfonated polyethylene and hydroperoxide are included in onepolymer-in-monomer solution (the adhesive) and the DHP is added toanother formulated polymer-in-monomer solution (the activator). Thecompositions disclosed in the examples can be utilized in either manner,but for convenience are shown as single solution blends in order toidentify the proportions of the formulating components.

[0065] A promoter is an organic salt of a transition metal, such ascobalt, nickel, manganese or iron naphthenate, copper octoate, copperacetylacetonate, iron hexoate, or iron propionate. Promoters are used toenhance cure rate. Promoters, whose effect varies greatly from system tosystem are used in amounts up to about 1-2 weight percent, preferablyabout 1 part per million to about 0.5 weight percent. Most preferredamounts are from about 5 parts per million to about 0.5 percent byweight.

[0066] The most preferred free radical generating systems are (1) atertiary amine reacting with benzyl peroxide or another peroxide or (2)a DHP derivative in combination with a sulfonyl chloride compound and ahydroperoxide to induce room temperature free radical curing.

[0067] The compositions of this invention have been developed primarilyto improve the properties of adhesives. However, the improvementsthereby discovered make these products more useful than previousproducts of their class for repair materials, coatings, bulk casting andany number of other applications beyond adhesives.

[0068] A specific example is the bridge deck overlay applicationdiscussed in the Prior Art. The preferred major components of thisinvention, namely poly (methyl methacrylate), nitrile polymers andelastomers, and chlorinated polymers and elastomers individually andcollectively are inherently resistant to the adverse elements to whichsuch overlays are exposed. Moreover, these components can readily bealtered and adjusted in terms of amount and composition to optimizetheir adhesive, physical and chemical properties, all within the scopeof this invention. All of these characteristics and benefits that areimportant for adhesives, including the ability to bond composites and avariety of other materials without surface preparation, and permanentretention of elastic properties, are applicable to a number of otherapplications, one example of which is bridge deck overlays.

EXAMPLES

[0069] Materials and Components Utilized in Examples Tradename orDescription Source Designation or Function or Supplier NeoprenePolychloroprene elastomer DuPont Dow Elastomers Nipol ® Nitrileelastomer Zeon Chemicals MMA Methyl methacrylate monomer INEOS AcrylicsPARALOID ® MBS impact modifier Rohm & Haas Co. BTA 753MAA Methacrylicacid monomer INEOS Acrylics DMT N,N-Dimethyl-p-toluidine First ChemicalHET Hydroxyethyl toluidine Bayer AG 55% BPO Paste Benzoyl peroxide (55%)in Elf Atochem proprietary plasticizer mixture Akzo Nobel IPSSS208/SS214 Commercially available, IPS Corporation proprietaryComponent B benzoyl peroxide paste BLENDEX ® ABS solution grade resin GEPlastics ADG 21 Terlux ® Clear MABS molding resin BASF 2812TR LMA Laurylmethacrylate monomer Sartomer BLENDEX ® ABS impact modifier GE Plastics338 Tyrin ® Chlorinated polyethylene duPont Dow Elastomers Hycar ®Reactive liquid BD/AN polymer Noveon, Inc. Ricacryl ® Reactive liquidbutadiene Ricon Resins, Inc. polymer Kraton ® Styrene/butadiene blockKraton Polymers copolymer HyTemp ® Polyacrylate elastomer Zeon ChemicalsHypalon ® Chlorosulfonated polyethylene DuPont Dow Elastomers Reillcat ™Dihydropyridine derivative ReillyIndustries,Inc. ASY-2 Luperox ® Cumenehydroperoxide (CHP) Elf Atochem CU 90

[0070] Test Substrates Utilized in Examples

[0071] The following is a generalized description of test substratesused for the evaluation of the adhesives of this invention. Specificdetails and identification of materials is provided in the specificexamples. Designation Description Source Steel AISI 1020 cold rolledsteel Various Aluminum 6061-T6 or as otherwise specified Various ABSPipe grade, rigid, 0.25 inch sheet Various PVC Type I rigid, 0.25 inchsheet Various Acrylic Plexiglas ®, 0.25 inch sheet Rohm & Haas FRP Openmolded fiberglass reinforced As specified polyester, inside or rawsurface Gel coat Outside, glossy show surface of As specified FRPcomposite, highly crosslinked Closed molded Polyester compositematerials produced composites by methods other than the open moldingprocess used to produce FRP composites SMC Polyester sheet moldingcompound As specified Pultrusion Test specimens cut form sheets or Asspecified profiles from pultrusion process using polyester resin RTMResin transfer molded polyester As specified

[0072] Formulation and Mixing Procedures Utilized in Examples

[0073] Unless otherwise indicated, the following procedure was used,employing techniques well known in the art, to prepare the experimentaladhesives:

[0074] Readily soluble or dispersible elastomers and resins weredissolved in methyl methacrylate (MMA) monomer in a jar or metal can ona laboratory roll mill to form stock solutions. The proportions ofpolymer and monomer were selected to provide a convenient workingviscosity to allow the addition and blending of successive formulationingredients. Typical solution concentrations in MMA of 15-35 percent byweight were selected to provide final solution viscosities ranging from50,000 to 200,000 cps. It is generally preferable to prepare the stocksolutions in the higher concentration and viscosity range in order to beable to make final viscosity adjustments by diluting the finishedadhesive with MMA monomer. The polymer and monomer were rolled until allof the polymer was dissolved and no lumps or particles of undissolvedmaterial were present.

[0075] Experimental adhesives were prepared in plastic beakers inquantities ranging from 100-300 grams of finished adhesive. Sufficientstock solution or a mixture of stock solutions was added to the beakerin the quantity required to provide the desired proportion of elastomerin the finished adhesive.

[0076] When powdered impact modifiers were added to the formulations,they were added to the polymer in monomer solution along with any othernon-catalytic liquid ingredients and mixed with a high shear laboratorymixer until a uniform, sometimes grainy paste consistency was achieved.The impact modifiers do not dissolve in the mixture, but rather swell togive the adhesive a gel-like consistency. Generally, two to four hoursis required for the impact modifier to swell and soften sufficiently tobe fully dispersed in the mixture. At this time, the adhesive is mixed asecond time under high shear to form a smooth paste. At the end of thesecond mix, the remaining ingredients are added and thoroughly mixedinto the adhesive.

[0077] Adhesives that do not contain an impact modifier were prepared byadding the remaining ingredients directly to the mixture of stockelastomer solutions and thoroughly mixed to form the finished adhesive.Final viscosity adjustments were made by adding with MMA monomer orfumed silica as required.

[0078] Preparation and Testing of Specimens from Examples Adhesive Bonds

[0079] Metal to metal lap shear bonds were prepared by bonding one inchby four inch test coupons with a nominal thickness of 0.060 inch to0.063 inch. A layer of adhesive was applied uniformly to each matingsubstrate coupon such that the adhesive completely covered the one-inchby one half-inch area at the end of the specimen. The amount of adhesiveis such that when the coupons are mated, there is sufficient excess thatthere is squeeze out around the entire perimeter of the bonded area toassure a fully bonded specimen.

[0080] The specimens were aligned in a metal fixturing mold in aparallel manner with one half-inch overlap with a uniform bond thicknessof 0.006-0.010 inch, depending on the thickness of the coupon. Excessadhesive squeeze out was carefully removed without disturbing the bondwhile the adhesive was still liquid. The bonds were left undisturbed forsufficient time for the adhesive to cure.

[0081] The metal adhesive bonds were tested according to ASTM methodD1002.

[0082] Adhesive lap shear bonds were prepared from plastic and compositesamples, either bonded to themselves or to metal test pieces, bysimilarly applying adhesive to either one half square inch or one squareinch areas at the end of each of two substrate pieces. The compositesubstrate pieces often vary in thickness. A nominal bond thickness wasachieved by using stainless steel wire spacing shims, and strips ofplastic to position the bonded specimens so that the specimens arealigned in a uniformly parallel manner.

[0083] The bonds were tested and the results reported according to ASTMmethod D5868.

[0084] In some cases, the thickness of the plastic substrates was suchthat the bonds were tested in compressive shear. Test specimens were cutand assembled according to test method D2564. The test method wasmodified in that following the application of adhesive to the testspecimens, stainless steel wire shims were used to provide a bond linethickness of approximately 0.010 inch if the bonding surfaces wereparallel and smooth. When bonding plastic specimens with rough or unevensurfaces, thicker wire spacers or some other method of maintaining anacceptable bond thickness was used. In any case, each example refers tothe test method used as well as any treatment used to prepare thesurfaces prior to bonding.

[0085] When reporting lap shear bond strength results, the followingabbreviations are used throughout the examples for the correspondingfailure modes:

[0086] AF: ADHESIVE FAILURE. The adhesive cleanly separates from thesubstrate surface.

[0087] CF: COHESIVE FAILURE. Failure occurs in the adhesive layer,leaving a distinct layer of adhesive on each substrate surface.

[0088] TLCF: THIN LAYER COHESIVE FAILURE. The failure appears to beadhesive in nature, with the bulk of the adhesive on one surface and athin residue of adhesive on the other.

[0089] FT or DL: FIBER TEARING OR DELAMINATION of composite substrates.

[0090] SF: Fracture failure and separation of the composite substrate atthe adhesive bondline, with no bond separation.

[0091] Bulk Tensile Properties of the Adhesive of the Examples

[0092] The improvements in the retention of elasticity of thecompositions of this invention were determined by measuring the bulkstress-strain properties of the adhesive according to ASTM test methodD638. Test specimens were prepared by mixing a sufficient quantity ofadhesive to prepare a uniformly flat film of adhesive approximately 6 to7 inches in diameter and 0.0625 inches thick. One of two methods wasused to prepare mix the adhesive for the films.

[0093] In the first method, the adhesive components were combined in thespecified ratios by simple hand mixing in a beaker. After the adhesivewas thoroughly mixed, the beaker was placed in a vacuum chamber andvacuum was applied in an intermittent fashion to remove air until thelast one or two applications of vacuum did not produce additionalfrothing or expansion. The adhesive was then transferred to one of twoglass or plastic plates approximately 12 inches in diameter with asimilar sized layer of Mylar release film on top of it. The adhesive wasplaced in the center of the film, and a mating Mylar film and plate wereplaced over the adhesive and pressed down uniformly to spread the film.Metal shims were placed around the perimeter of the plates to establishthe desired film thickness.

[0094] In the second method, commercial or experimental adhesives weredispensed in the center of the film plates from commercial plasticcartridges, such as those sold by the Mix Pac Company, through a staticmixer provided by the same manufacturer. Experimental adhesivecomponents were individually degassed, as described above, prior topreparing the samples.

[0095] A variation of this method is to mix and degas the adhesive asindicated above and quickly transfer it to a single component caulkingcartridge to dispense it on the film plates.

[0096] After the films were cured, the plates were removed. Testdumbbells were cut from the films as specified in the test method,taking care to cut the specimens from the most void-free section of thefilm. The films were allowed to cure for the indicated period of time atambient temperature or at elevated temperatures as indicated in theexamples prior to cutting the dumbbells. Each test number is the averageof at least eight, and typically ten individual test specimens.

[0097] In the following examples, the adhesive components were preparedand mixed as indicated above. Unless otherwise specified, all indicatedproportions are percent by weight.

Example 1

[0098] The results in Table 1 illustrate the improvement in tensileproperties of adhesive compositions, especially tensile elongation,through the addition of nitrile elastomers to adhesives containingpolychloroprene or neoprene. Comparative Example 1A is a preferred priorart composition disclosed in U.S. Pat. No. 5,206,288, wherein the BTA753 impact modifier contains approximately 70-80 percent polybutadiene,with a Tg of approximately −80° C. In Inventive Examples 1B and 1C, thetotal amount of elastomer or elastomer containing polymer is the same asthat of Comparative Example 1A. In Inventive Example 1D, the totalamount of elastomer is less than that of Comparative Example 1A. TABLE 1(Comparative) EXAMPLE Tg, ° C. 1A 1B 1C 1D Neoprene AD-10 −39 10.00 7.507.50 9.25 Nipol DN 4555 −10 — 7.50 — — Nipol DN 401LL est. −38 — — 7.5013.88 MMA Monomer 64.50 64.50 64.50 71.37 Paraloid 20.00 15.00 15.00 —BTA 753 Methacrylic Acid 5.00 5.00 5.00 5.00 HET 0.50 0.50 0.50 0.50100.00 100.00 100.00 100.00 55% BPO Paste 2.50 2.50 2.50 2.50 TensileProperties ASTM D638 24 Hours Room Temperature Stress at Failure (psi)3777 3550 3645 3005 Elongation (%) 179 183 219 122 24 Hours RoomTemperature + 1 Hour at 82° C. Stress at Failure (psi) 4077 4437 40233209 Elongation (%) 80 120 134 87

[0099] Inventive Examples 1B-1D illustrate a number of unexpectedresults. In Example 1B, a portion of the Neoprene, with a Tg of −35degrees C., and BTA 753, with estimated polybutadiene content of 70percent and Tg of −80 degrees C. is replaced with a nitrile polymer witha Tg of −10 degrees and a butadiene content of 55 percent. In spite ofthe overall reduction in the Tg of the elastomeric content and thepolybutadiene content of Example 1B, it exhibits slightly higher initialtensile elongation and significantly higher retained elongation than theprior art Comparative Example 1A. This is unexpected. The composition ofExample 1C, wherein the same proportion of total elastomeric componentof Comparative Example 1A is replaced with a nitrile polymer with a lowglass transition temperature and higher polybutadiene content provideseven greater initial and retained elongation, even though the overallelastomer content is not increased. In Example 1D, the preferred BTA 753component is entirely removed and replaced with a lesser amount ofnitrile elastomer with similar butadiene content. In spite of thisoverall reduction in the level of elastomeric components, the curedcomposition remains more elastic than Comparative Example 1A followingexposure to 82° C. for one hour.

Example 2

[0100] The results in Table 2 illustrate improvements in tensileproperties, especially tensile elongation, through the addition ofnitrile elastomers to adhesives containing polychloroprene or neopreneand ABS impact modifier in place of an MBS impact modifiers. Theseexamples also contain a long chain methacrylate monomer, laurylmethacrylate. Comparative Example 2A is similar to Comparative Example1A above, except that the BTA 753, an MBS impact modifier has beenreplaced with Blendex 338, an ABS impact modifier with a similarly highpolybutadiene content. The Inventive Examples are Examples 2B, 2C, 2Dand 2E. TABLE 2 (Comparative) EXAMPLE 2A 2B 2C 2D 2E Neoprene AD-1011.40 11.40 7.50 12.00 7.50 Nipol DN 4555 — — — 5.67 7.50 Nipol DN 401LL— — 7.50 — — BLENDEX ADG-21 — 20.00 — 11.33 — MMA Monomer 58.10 58.1059.50 68.00 59.50 Lauryl Methacrylate 5.00 5.00 5.00 5.00 5.00 Blendex338 20.00 — 15.00 — 15.00 Methacrylic Acid 5.00 5.00 5.00 4.00 5.00 HET0.50 0.50 0.50 0.50 0.50 DMT — — — 0.55 — Total 100.00 100.00 100.00100.00 100.00 55% BPO Paste 2.50 2.50 2.50 — 2.50 IPS SS214 Component B(Proprietary BPO Paste) 10:1 V/V* Tensile Properties ASTM D638 24 HoursRoom Temperature Stress at Failure (psi) 3565 3709 3304 2844 3511Elongation (%) 176 65.7 184 147 145 24 Hours Room Temperature + 1 Hourat 82° C. Stress at Failure (psi) 3857 3833 3771 2777 4086 Elongation(%) 60.1 29.8 112 151 63.1

[0101] Example 2C illustrates that the addition of a nitrile elastomerwith low acrylonitrile content and low Tg provides considerableimprovement over Comparative Example 2A. Example 2D illustrates that thecombination of polychloroprene, a nitrile polymer with a high Tg and ABSsolution grade resin can be formulated to provide excellent retention ofelastic properties compared with the prior art.

Example 3

[0102] The results in Table 3 illustrate significant improvements in theelongation of prior art adhesive compositions based on an MBS impactmodifier and chlorinated polyethylene when a relatively small amount ofa reactive liquid butadiene-acrylonitrile is added to the composition.The first example of each of 3A, 3B and 3C in a comparative examplewhile the second and third examples of Examples 3B and 3C are InventiveExamples. TABLE 3 EXAMPLE 3A 3B 3C Tyrin 3611P 36% Cl 12.00 12.00 12.00Tyrin 3615P 36% Cl 12.00 12.00 12.00 Tyrin 4211P 42% Cl 12.00 12.0012.00 MMA Monomer 69.60 67.10 64.60 69.60 67.10 64.60 69.60 67.10 64.60PARALOID BTA 753 18.00 18.00 18.00 18.00 18.00 18.00 18.00 18.00 18.00Hycar 1300X33 18% ACN 2.50 2.50 2.50 Hycar 1300X43 22% ACN 2.50 2.502.50 HET 0.40 0.40 0.40 0.40 0.40 0.40 0.40 0.40 0.40 Total 100. 100.100. 100. 100. 100. 100. 100. 100. 55% BPO Paste 2.50 2.50 2.50 2.502.50 2.50 2.50 2.50 2.50 Tensile Properties ASTM D638 24 Hours RoomTemperature + 1 Hour at 100° C. Stress at Failure (psi) 3650 3648 35373291 3242 3261 4204 3848 3835 Elongation (%) 33.3 92.3 108 54.3 121 13232.6 122 116

Example 4

[0103] The results in Example 4 further illustrate that the nitrilegroup is important in the elastomeric components of the presentinvention in providing the advantages of increased elongation of thecured adhesives. As shown in Table 4, the addition of a liquidpolybutadiene resin with no nitrile groups in the backbone does notprovide as much increase in the initial elongation of compositionssimilar to those of Example 3. No heat aging tests were performed withthese examples because of the relatively lower initial elongation. TABLE4 EXAMPLE 4A 4B 4C 4D 4E 4F Tyrin 3611P 12.00 12.00 Tyrin 3615P 12.0012.00 Tyrin 4211P 12.00 12.00 PARALOID BTA-753 18.00 18.00 18.00 18.0018.00 18.00 MMA Monomer 67.10 64.60 67.10 64.60 67.10 64.60 Ricacryl3500 2.50 5.00 2.50 5.00 2.50 5.00 HET 0.40 0.40 0.40 0.40 0.40 0.40Total 100.00 100.00 100.00 100.00 100.00 100.00 55% BPO Paste 2.50 2.502.50 2.50 2.50 2.50 Tensile Properties ASTM D638 24 Hours RoomTemperature Stress at Failure (psi) 4028 3734 3582 3633 4780 4881Elongation (%) 48 44 71 61 46 61

Example 5

[0104] The results in Table 5 further illustrate improvements in tensileelongation through the addition of solid nitrile elastomers to adhesivescontaining chlorinated polyethylene as the chlorinated polymer componentof the adhesive composition. The elastomer blends are compared with ablend disclosed in Comparative Example 5A containing chlorinatedpolyethylene and an ABS impact modifier. The Inventive Examples areExamples 5B, 5C and 5D. TABLE 5 (Comparative) EXAMPLE 5A 5B 5C 5D Tyrin4211P 12.00 12.00 12.00 12.00 Nipol DN 1201L* — 15.00 — — Nipol DN1401LG — — 15.00 — Nipol 401LL — — — 15.00 MMA Monomer 57.50 62.50 62.5062.50 Lauryl Methacrylate 5.00 5.00 5.00 5.00 Blendex 338 20.00 — — —Methacrylic Acid 5.00 5.00 5.00 5.00 HET 0.50 0.50 0.50 0.50 Total100.00 100.00 100.00 100.00 55% BPO Paste 2.50 2.50 2.50 2.50 TensileProperties ASTM D638 24 Hours Room Temperature Stress at Failure (psi)4736 3895 4594 3503 Elongation (%) 93.6 148 120 106 24 Hours RoomTemperature + 1 Hour at 82° C. Stress at Failure (psi) 5330 4843 51113230 Elongation (%) 47.4 111 85.4 75.1

[0105] Example 5B shows that a butadiene/isoprene/acrylonitrileterpolymer is especially effective in combination with the specificchlorinated polyethylene employed. It is noteworthy that the Nipol 401LL, the nitrile elastomer with the highest butadiene rubber content(81%) and the lowest Tg (est. −38° C.) in the group, does not providethe greatest degree of elasticity. This provides additional confirmationof the importance of the nitrile content of the polymer blends in thisinvention.

Example 6

[0106] The results in Table 6 demonstrate the application of thisinvention and improvement in elastic properties over the prior art withcompositions based on chlorosulfonated polyethylene as the chlorinatedpolymer and employing cumene hydroperoxide and a dihydropyridine basedactivator component. Example 6A is a Comparative Example and Examples6B, 6C and 6D are Inventive Examples. TABLE 6 (Comparative) EXAMPLE 6A6B 6C 6D Hypalon 30 10.00 10.00 7.50 7.50 Nipol DN 4555 — — 7.50 — NipolDN 401LL — — — 7.50 MMA Monomer 66.50 71.50 64.50 66.50 PARALOID KM 75318.00 18.00 15.00 13.00 Methacrylic Acid 5.00 — 5.00 5.00 Reillcat ASY-22.00 2.00 2.00 2.00 Cumene Hydroperoxide 0.50 0.50 0.50 0.50 100.00100.00 100.00 100.00 Tensile Properties ASTM D638 24 Hours RoomTemperature Stress at Failure (psi) 3298 3476 3018 3290 Elongation (%)107 128 171 168 24 Hours Room Temperature + 1 Hour at 82° C. Stress atFailure (psi) 5980 5644 5562 5321 Elongation (%) 44.4 24.4 68.4 70.3

[0107] When compared with the prior art examples 6A and 6B, examples 6Cand 6D of the present invention show significant increases in initialelongation. They also retain significantly higher elongation afterexposure to 1 hour at 82° C.

Example 7

[0108] The results in Table 7 compare the stress/strain properties ofrepresentative commercial methacrylate adhesives with those of thepresent invention with room temperature cure and following various heatcycles. While the heat cycles differ from sample to sample, the trendsare evident. It is clearly shown that the adhesives of the presentinvention provide substantial improvements over the commercial products.Examples 6E and 6F illustrate the utility of ABS and MABS solution andmolding grade resins in the compositions of this invention. ComparativeExamples are Examples 7A, 7B, 7C and 7D and Inventive Examples areExamples 7E, 7F, 7G and 7H. TABLE 7 Comparative Examples EXAMPLE 7A 7B7C 7D COMMERCIAL ADHESIVES 1) DHP Cure, 1:1 mix ratio general ▾ purposestructural methacrylate 2) BPO Cure, 4:1 mix ratio ▾ methacrylateadhesive for metal 3) BPO Cure, 10:1 mix ratio all ▾ purpose structuralmethacrylate 4) 1:1 Mix ratio polyurethane ▾ adhesive for composites 7E7F 7G 7H FORMULATED ADHESIVES Hypalon 30 7.50 11.79 11.79 — NeopreneAD-10 — — — 12.00 Nipol DN 4555 — 7.40 7.40 5.67 Nipol 401LL 7.50 — — —Terlux 2812TR (MABS) — 3.30 3.30 — Blendex ADG-21 (ABS) — — — 11.33 MMAMonomer 66.50 66.57 59.09 68.00 Lauryl Methacrylate — — 7.50 5.00PARALOID KM 753 13.00 5.80 5.80 — Methacrylic Acid 5.00 4.40 4.40 4.00Reillcat ASY-2 2.00 2.50 2.50 — Cumene Hydroperoxide 0.50 0.36 0.36 —BHT — 0.36 0.36 — DMT — — — 0.55 IPS SS214 Component B — — — 10:1(Proprietary BPO Paste) V/V* Comparative ASTM D638 7A 7B 7C 7D 7E 7F 7G7H 24 Hours Room Temperature Stress at Failure (psi) 3688 1913 n.t. 26543290 3665 2330 2844 Elongation (%) 140 58.5 n.t. 62.6 169 179 232 147Hours 3 2 4 1 1 1 1 1 24 Hours Room Temperature + Heat Cycle Temperature° C. 59 93 70 100 82 82 82 82 Stress at Failure (psi) 5873 2593 26043049 5321 5069 3973 2777 Elongation (%) 36.9 26.3 32.5 62.7 70.3 112 165151

[0109] The results clearly show the substantial improvements in originaland retained elongation of the adhesives of the present invention overthe commercial methacrylate adhesives.

[0110] It is also noteworthy that the retained elongation of all of theformulated methacrylate adhesives exceeds that of the commercialpolyurethane, and that some far exceed the elastic properties of thepolyurethane.

[0111] Examples 8 through 13 illustrate the unique ability of thecompositions of this invention to bond a variety of composite materials,including difficult to bond closed molded composites, with minimalsurface preparation.

Example 8

[0112] Example 8 illustrates improvements in the ability to bond acommercial grade of sheet molded composite (SMC) used in the fabricationof buses. The performance of the improved adhesives of this inventionwas compared with (1) commercial methacrylate adhesives with a 10 to 1mix ratio and (2) formulated adhesives individually containingpolychloroprene and nitrile elastomers. See Table 8. ComparativeExamples are Examples 8A-8E, and Examples 8F and 8G are InventiveExamples. TABLE 8 (Comparative Examples) EXAMPLE 8A 8B 8C 1) CompetitiveMethacrylate A ▾ Adhesive 12 Minute Cure Contains Chlorinated Polymer 2)Competitive Methacrylate B ▾ Adhesive 40 Minute Cure ContainsChlorinated Polymer 3) IPS SS 208 Methacrylate ▾ Contains NitrilePolymer (Comparative) FORMULATED ADHESIVE 8D 8E 8F 8G Neoprene AD-1018.00 — 8.00 12.50 Nipol DN 401LL — 18.00 8.00 12.50 MMA Monomer 77.0177.01 77.01 70.90 Methacrylic Acid 4.50 4.50 4.50 — HET 0.30 0.30 0.300.35 DMT 0.11 0.11 0.11 0.11 Fumed Silica — — 1.00 2.00 Paraffin Wax0.65 Disparlon 6200 — — 1.25 — (Organic Thixotrope) IPS SS208 ComponentB 10:1 (Proprietary BPO Paste) V/V Lap Shear Strength ASTM D5868 SurfacePreparation: None Bond Thickness (in): 0.025 8A 8B 8C BD 8E 8F 8G ShearStress at 543 742 282 448 534 762 936 Failure Failure Mode AF AF/FT AFAF AF FT SF 100%

[0113] When compared with commercial or formulated adhesives thatindividually contain chlorinated or nitrile polymers, but not thecombination, examples 8F and 8G containing the blend show significantimprovements in adhesion to the difficult substrate as evidenced by 100%fiber tearing bonds or complete failure of the composite specimen withno separation of the bond at all.

Example 9

[0114] Example 9 illustrates improvements in the ability to bond adevelopmental grade of pultruded composite based on Reichhold polyesterresin 31615. The performance of the improved adhesives of this inventionwas compared with commercial methacrylate adhesives with a 10 to 1 mixratio. See Table 9. Examples 9A, 9B and 9C are Comparative Examples, andExample 9D is an Inventive Example. TABLE 9 Comparative Examples EXAMPLE9A 9B 9C 9D 1) Competitive Methacrylate B ▾ 2) Competitive MethacrylateC ▾ Adhesive 20 Minute Cure Contains Chlorinated Polymer 3) IPS SS 208Methacrylate ▾ Contains Nitrile Polymer FORMULATED ADHESIVE NeopreneAD-10 12.5 Nipol DN 401LL 12.5 MMA Monomer 66.9 Methacrylic Acid 4.50HET 0.35 DMT 0.11 Fumed Silica 2.00 Paraffin Wax 0.65 IPS SS208Component B 10:1 (Proprietary BPO Paste) V/V* *Mix ratio by volume ofadhesive and BPO paste. Lap Shear Strength ASTM D5868 SurfacePreparation None None None None Bond Thickness (in) 0.125 0.125 0.1250.125 Shear Stress at Failure 698 320 386 1107 Failure Mode AF/FT AF AF100% FT

[0115] As in Example 8, the adhesive of the present invention provides amuch higher level of adhesion over the commercial adhesives thatindividually contain chlorinated or nitrile polymers, but not thecombination.

Example 10

[0116] Example 10 illustrates improvements in the ability to bond acommercial grade of pultruded composite used for an adhesively bondedgas pipeline repair system. The performance of the improved adhesives ofthis invention was compared with the commercial methacrylate adhesivesupplied with the repair system. The surface of the composite is veryshiny and inert, and difficult to bond with any adhesive without somedegree of surface preparation. Light buffing with an abrasive pad thatjust removes the gloss is sufficient to promote adhesion, and thistreatment was done with both adhesives tested. See Table 10. Examples10A is a Comparative Example and Example 10B is an Inventive Example.TABLE 10 (Comparative) EXAMPLE 10A 10B Commercial Repair Adhesive ▾FORMULATED ADHESIVE Neoprene AD-10 9.3 Nipol DN 401LL 9.3 MMA Monomer77.3 HET 0.35 DMT 0.11 Fumed Silica 2.00 Paraffin Wax 0.65 55% BPO Paste3.5 Lap Shear Strength ASTM D5868 Surface Preparation Buff Buff BondThickness (in) 0.025 0.025 Shear Stress at Failure 1456 3409 FailureMode CF FT/CF

[0117] In this case, it is possible to take advantage of the increasedcohesive strength and improved adhesion capability of the presentinvention to provide a much higher stress to failure of the bond. Thishas the potential of increasing allowable service life or severity ofservice conditions of repairs utilizing bonded composite systems of thistype.

Example 11

[0118] Example 11 illustrates improvements in the ability to bond acommercial grade of SMC composite used in the manufacture ofrecreational vehicles. In the molding process, a liberal amount ofChemlease 41-90, a hydrocarbon-based mold release is used to preventmold fouling and sticking. The residual mold release makes it especiallydifficult to bond the composite without surface preparation. Theperformance of the improved adhesives of this invention was comparedwith commercial methacrylate adhesives with a 10 to 1 mix ratio. In thisexample, the composite is bonded to aluminum, and the bond failureoccurs at the composite surface or in the composite substrate. No known,commercially available adhesive is fully capable of reliably bondingthis specific composite treated with the indicated mold release. SeeTable 11. Example 11A is a Comparative Example and Example 11B is anInventive Example. TABLE 11 (Comparative) EXAMPLE 11A 11B CommercialAdhesives A-C ▾ and IPS SS 208 FORMULATED ADHESIVE Neoprene AD-10 12.5Nipol DN 401LL 12.5 MMA Monomer 66.9 HET 0.35 DMT 0.11 Fumed Silica 2.00Paraffin Wax 0.65 55% BPO Paste 4.50 Lap Shear Strength ASTM D5868Surface Preparation None None Bond Thickness (mils) 0.125 0.125 ShearStress at Failure 175-180 560 Failure Mode AF FT (100%)

[0119] As shown in Example 11B, a preferred composition of the presentin invention provides greatly improved adhesion to this difficultsurface and create a 100 percent fiber-tearing structural bond.

Example 12

[0120] Example 12 illustrates improvements in the ability to bondaluminum with the adhesives compositions of this invention. The specificgrade of aluminum tested (Examples 12A-12C) is used for the structuralfabrication of busses in combination with the SMC sheet described inExample 8. It is important to be able to reliably bond the SMC andaluminum surfaces together in this application. The specific aluminumalloy is not known. It is referred to as “Ex. 8”. For the purpose ofthis example, the aluminum is bonded to itself rather than the weakerSMC substrate to fully evaluate the strength of the aluminum bond. SeeTable 12. Examples 12A and 12B are Comparative Examples and Example 12Cis an Inventive Example. TABLE 12 Comparative EXAMPLE 12A 12B 12CCompetitive Methacrylate B ▾ IPS SS 208 Methacrylate ▾ FORMULATEDADHESIVE Neoprene AD-10 12.5 Nipol DN 401LL 12.5 MMA Monomer 66.9Methacrylic Acid 4.50 HET 0.35 DMT 0.11 Fumed Silica 2.00 Paraffin Wax0.65 IPS SS208 Component B 10:1 (Proprietary BPO Paste) V/V Lap ShearStrength ASTM D5868 Surface Preparation: None Bond Thickness (in) 0.025Shear Stress at Failure 1302 1329 1999 Failure Mode AF AF CF

[0121] It is clearly evident that the adhesive of the present inventionprovides greatly improved adhesion to the aluminum surface as evidencedby the higher bond strength and cohesive failure of the bond. This,combined with the improved adhesion to the mating SMC substrateexhibited in Example 8, illustrates the value of the adhesives of thisinvention for bonding difficult combinations of materials.

Example 13

[0122] The results in Table 13 demonstrate the broad range of bondingcapability of the adhesives of this invention. TABLE 13 FORMULA 13 13Hypalon 30 11.00 Nipol DN 4555 4.00 Terlux 2812TR 6.00 MMA Monomer 63.70PARALOID KM 753 8.00 Methacrylic Acid 4.00 Reillcat ASY-2 2.50 CumeneHydroperoxide 0.40 BHT 0.40

[0123] All of the following substrates were bonded in the as receivedcondition with no surface preparation prior to bonding. C. R 6061 T6Stainless FRP/ Gel/ Gel/ Steel Aluminum Steel (304) Wood Wood Gel ABSPVC Plexiglass Lap Shear Strength 3050 258 2175 ASTM D1002 AF/CF AF AFLap Shear Strength 301 355 583 ASTM D5868 SF (W) SF (W) FT (100%)Compressive Shear 1259 3657 3404 Strength ASTM D2564 LCF CF/TLCF TLCF

[0124] The results show that the compositions of the present inventioncan be used to bond a variety of materials used in product assemblyprocesses. In this case, the adhesive composition is one that emphasizesbonding capability with ferrous metals and a wide variety ofnon-metallic substrates, including plastics and other materials. Whenrequired, adhesion of compositions such as is shown in the formulationof Example 13 can be improved on aluminum, stainless steel and othermetals through the use of surface treatments well known to those skilledin the art.

[0125] While the invention has been described in terms of variouspreferred embodiments, these should not be construed as limitations onthe scope of the invention. Many other variations, modifications,substitutions and changes may be made without departing from the spiritthereof.

1. An adhesive composition comprising a mixture of about 1 percent toabout 50 percent by weight of a chlorinated polymer, about 0.5 percentto about 45 percent by weight of a nitrile elastomer, a thermoplasticacrylonitrile copolymer or mixtures thereof, and about 25 percent toabout 90 percent by weight of an alkyl acrylate or methacrylate monomer.2. An adhesive composition comprising a mixture of about 2 percent toabout 40 percent by weight of a chlorinated elastomer polymer, about 0.5percent to about 25 percent by weight of a nitrile elastomer, athermoplastic acrylonitrile copolymer or mixtures thereof, and about 40percent to about 90 percent by weight of a C₁ to C₅ alkyl acrylate ormethacrylate monomer.
 3. An adhesive composition comprising a mixture ofabout 5 percent to about 30 percent by weight of a chlorinated elastomerpolymer, about 0.5 percent to about 20 percent by weight of a nitrileelastomer, a thermoplastic acrylonitrile copolymer or mixtures thereof,and about 50 percent to about 85 percent by weight of a C₁ to C₅ alkylacrylate or methacrylate monomer.
 4. The composition of claims 1, 2 or 3in admixture with from about 0.01 up to about 25 percent by weight C₆ orhigher acrylate or methacrylate monomer.
 5. The composition of claims 1,2 or 3 in admixture with from about 0.01 to about 30 percent by weightof a core shell impact modifier.
 6. The composition of claims 1, 2 or 3in admixture with from about 0.01 to about 15 percent by weight of apolymerizable organic acid monomer.
 7. The composition of claims 1, 2 or3 in admixture with a free radical generating catalyst system.
 8. Thecomposition of claims 1, 2 or 3 in admixture with a catalyst promoter.9. The composition of claims 1, 2 or 3 in admixture with a C₆ or higheracrylate or methacrylate monomer and a core shell impact modifierpolymer.
 10. The composition of claims 1, 2 or 3 in admixture with a C₆or higher acrylate or methacrylate monomer and a polymerizable organicacid monomer.
 11. The composition of claims 1, 2 or 3 in admixture witha C₆ or higher acrylate or methacrylate monomer and a free radicalgenerating catalyst system.
 12. The composition of claims 1, 2 or 3 inadmixture with a core shell impact modifier polymer and a free radicalgenerating catalyst system.
 13. The composition of claims 1, 2 or 3 inadmixture with a free radical generating catalyst system and a catalystpromoter.
 14. The adhesive composition of claim 1 wherein thechlorinated polymer comprises a polyvinyl chloride.
 15. The adhesivecomposition of claim 1 wherein the chlorinated polymer comprises apolyvinyl chloride or a blend of a polyvinyl chloride and a nitrileelastomer.